[The activity] was [from] a non-seismic zone, therefore judging from the time and location of the event, it might be related to the missing MH370 flight. If it was indeed an airplane crashing into the sea, the seismic wave strength indicated that the crash process was catastrophic.

Chinese seismologists noticed a suspicious event they speculated could be a plane crashing hard into the Ocean. [Image Source: Univ. of Science and Technology, China]

But the Boeing Comp. (BA) Boeing 777 had a backup communications system at a low level, as many had speculated. That system -- the Aircraft Communications Addressing and Reporting System (ACARS) -- was active during Flight 370's mysterious journey.

The ACARS system on the plane is manufactured and served by Inmarsat plc (LON:ISAT), a UK satellite company. Inmarsat systems are in roughly 90 percent of long haul passenger planes worldwide.

The version of ACARS on the plane is basic, but more sophisticated versions include satellite messaging systems. However, Malaysia Airlines System Bhd (MK:MAS) -- the firm that owns and operates Malaysian Airlines -- opted not to pay for that feature.

The ACARS appeared a dead end on Thursday when The Wall Street Journalreported:

Malaysia Airlines CEO Ahmad Jauhari Yahya said that based on the airline's records, the last transmission was at 1:07 a.m. Saturday, slightly earlier than the time that officials have said the airliner disappeared from radar as it was flying northward over the South China Sea.

According to other reports, the plane's transponder fell silent at 1:21 a.m.

Combined with the Chinese seismology report, it would be easy to come to the premature conclusion that something horrible had happened in flight, and that systems quickly failed.

II. Transponder was Powered; But Someone or Something Silenced it

The mystery continued to mount today when sources began to indicate that The Wall Street Journal report was misleading or inaccurate. It turns out the ACARS system was actually switched off. However, you can't fully disable the system. So when the satellite it was communicating with sent it pings, the plane answered back for the next several hours.

David Coiley, vice president of aviation products at Inmarsat, is quoted byThe Guardian as saying:

When the system is not transmitting or receiving data on the aircraft, it will send network signalling info to establish that the aircraft satellite communication is switched on, to say that the system could communicate. If we haven’t seen any activity from an aircraft or ship it’s a check. It’s a simple acknowledgement.

The ping doesn’t say anything other than that the satellite communications is functioning.

The plane had seven hours worth of fuel. [Image Source: The Washington Post]

In other words, the plane clearly had power for hours after it fell silent. The plane was traveling with seven hours worth of fuel, which would allow it to reach many destinations in Southeast Asia and the Middle East.

More evidence came via Wednesday's reports that military radar posts in Thailand picked up an unknown aircraft was traveling at 30,000 feet at 2:15 a.m., headed due west towards the Bay of Bengal.

The estimated flight path [Image Source: NY Daily News]

On Friday CNN reported that a classified analysis by the U.S. military intelligence, Malaysian government, and other cooperating nations indicated that the plane's ACAR system stopped responding to pings around five hours after taking it off. That means it likely could not reach the Middle East (which is further evidenced by the fact that such a path would be picked up by radar in India).

Very recent reports state that the plane climbed to 40,000+ feet -- an unauthorized altitude -- before plunging "unevenly" to an altitude of 23,000 feet and passing over Thailand. The airplane then climbed up to the aforementioned altitude of 30,000 feet.

Some have speculated the altitude changes could be signs of a struggle in the pilot's cabin.

Some have speculated that pirates could have landed the airplane on the Andaman and Nicobar Islands, which are owned by India and have a runway long enough to support the landing. But Denis Giles, editor of the Andaman Chronicle, blasted that suggestion, stating:

There is no chance, no such chance, that any aircraft of this size can come towards Andaman and Nicobar Islands and land.

Aviation experts say there's a small chance the plane crash landed on an abandoned island in the Nicobar or Andaman Islands. [Image Source: The Guardian]

But aviation experts say otherwise. They claim there's a slim chance also that the plane may have performed an emergency landing in the Adaman and Nicobar Islands. While such a landing would be daunting, only 37 of the 572 islands are inhabited, according to The Guardian. Indian authorities are now scouring the island's jungles.

III. Hijacking… or Something Else?

The incident has raised suspicions that the airline was hijacked. Initial scrutiny turned to two Iranians traveling with stolen passports. But the plane's western diversion closely followed local waypoints by pilots when traveling on routes to Europe.

That suggests whoever was flying on the plane was a professional pilot, and likely one who had flown in the region.

Now scrutiny is focusing on the pilots.

A banner was signed by many well wishers and friends of the crew and passengers.
[Image Source: Reuters]

Two Australian women -- Jonti Roos and Jaan Maren -- both claim that the younger 27-year-old pilot -- Fariq Abdul Hamid -- had invited them into the cockpit for the course of their 2011 flight and was behaving boisterously. Comments Ms. Roos:

Throughout the whole flight they were talking to us, they were actually smoking throughout the flight, which I don’t think they’re allowed to be doing and they were taking photos with us in the cockpit while they were flying the plane.

Ms. Roos said the pilots invited her and her friend to stay with him at his place in Malaysia. She said she felt the invitation seemed "possibly a little bit sleazy" and she and her friend declined.

But Mr. Fariq's friends attacked that report saying that the young pilot was a devout, religious Muslim (as was the older pilot). APinterviewed his neighbor, Ayop Jantan, who said he was engaged and scheduled to be married soon.

But clearly the incident in question did happen as Ms. Roos released a photograph that showed herself in the cockpit with Mr. Hamid. The pilot also shows her friend, Ms. Maree wearing the pilot's hat.

Whether it was a hijacking or something even more bizarre, U.S. and Malaysian authorities believe the most likely possibility is that the plane crashed into the ocean. Based on the signals they estimated that it either traveled south or headed northwest across the Bay of Bengal, which would place it crashing near India.

Oh and that earthquake? According to the U.S. Geological Survey (USGS) the Chinese seismologists goofed up. Their analysis of the data showed it really was a small earthquake, which they said measured magnitude 2.7 on the Richter scale.